S. Seol, A. Sharp, and P. Kim. Proceedings of WORLDCOMP'11: The 2011 World Congress in Computer Science, Computer Engineering, and Applied Computing, (2011)
M. Maifarth, J. Griesbaum, and R. Kölle. E-Learning zwischen Vision und Alltag, Medien in der Wissenschaft, 64, page 332-337. Münster, New York, München,Berlin, Waxmann, (2013)